1. Field of the Invention
The present invention relates to a valve for a gas circuit breaker, and particularly, to a valve for a gas circuit breaker capable of cutting off a current or controlling gas flow in a circuit breaker.
2. Background of the Invention
A circuit breaker indicates a protection device which provides power by being operated as a conductor in an ordinary time, but rapidly cuts off a current when an accident occurs. A gas circuit breaker indicates a circuit breaker using gas as a medium to perform cut off and insulation.
This gas circuit breaker adopts therein a plurality of valves for controlling gas flow. In a case of a serial automatic expansion type circuit breaker, used is a valve configured to allow gas flow when gas has a pressure difference more than a specific value with respect to one direction, and to allow gas flow even when gas has a small pressure difference with respect to another direction. Rapidly operating the valve greatly influences on enhanced performance and reliability of the circuit breaker.
FIGS. 1 and 2 show one example of a valve for a gas circuit breaker. Referring to FIGS. 1 and 2, the valve is installed in a cylinder 10 which forms appearance of the gas circuit breaker and providing a gas flow path therein. A valve fixing bracket 20 is disposed in the cylinder 10, and a sleeve 22 is disposed at a central part of the cylinder 10. The valve consists of a first blocking plate 30 and a second blocking plate 40, and passing holes 32 and 42 are respectively formed at the first blocking plate 30 and the second blocking plate 40 so as not to overlap each other. The valve fixing bracket 20 is disposed between the first and second blocking plates 30 and 40, and is provided with passing holes (not shown) communicated with the passing holes 32 and 42. Accordingly, when both of the first and second blocking plates 30 and 40 are in a closely contacted state to the valve fixing bracket 20, gas flow can not occur. On the other hand, when at least one of the first and second blocking plates 30 and 40 is separated from the valve fixing bracket 20, gas flow can occur.
The first and second blocking plates 30 and 40 are configured to be slidable along a fixing pin 50 in an inserted state to the fixing pin 50. The first blocking plate 30 receives an elastic force which is towards the second blocking plate 40 by a coil spring 52 disposed between the fixing pin 50 and a fixing flange 54. The fixing pin 50 is fixed to the valve fixing bracket 20.
The left side of FIG. 2 illustrates a case that a pressure of ‘A’ is higher than a pressure of ‘B’, and the right side of FIG. 2 illustrates an opposite case. If the pressure of ‘A’ is higher than the pressure of ‘B’, the second blocking plate 40 moves towards the first blocking plate 30 thus to closely contact the valve fixing bracket 20. The first blocking plate 30 closely contacts the valve fixing bracket 20 by an elastic force of the coil spring 52. Since both of the first and second blocking plates 30 and 40 closely contact the valve fixing bracket 20, gas flow can not occur.
If the pressure is gradually increased to be larger than the elastic force of the spring, the pressure is applied to the first blocking plate 30 through the passing holes 42 of the second shielding late 40. Accordingly, the first blocking plate 30 downwardly moves thus to be separated from the valve fixing bracket 20. As a result, gas inside ‘A’ is introduced into B′. On the other hand, if the pressure of ‘B’ is higher than the pressure of ‘A’, the first blocking plate 30 upwardly moves thus to closely contact the valve fixing bracket 20. Here, the second blocking plate 40 also upwardly moves to open a gas flow path, and gas inside ‘B’ is introduced into ‘A’.
However, the conventional valve for a gas circuit breaker may have the following problems.
The gas flow path is provided through the passing holes arranged at the first and second blocking plates so as to cross each other, thereby limiting an area of the gas flow path. More concretely, if the passing holes formed at one blocking plate are widened, the passing holes formed at another blocking plate have to be narrowed. This may cause a limitation in increasing an area of the gas flow path. As a result, a flow resistance of gas may be increased, and design degrees of freedom may be limited.